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Foreign Secretary William Hague today declared that stopping Syria becoming “the greatest humanitarian catastrophe of the 21st century” will top the G8 agenda.

Mr Hague made the comments as he and his counterparts from the world’s eight most powerful nations were meeting in London today.

He said Britain would be pressing its case for doing more to help the Syrian opposition against the regime of President Bashar al-Assad.

“I will be joining and convening some of those meetings to discuss the urgent humanitarian needs and the urgent need for a political and diplomatic breakthrough,” said Mr Hague.

“This is turning into the greatest humanitarian catastrophe of the 21st century so far and we cannot watch this happen.”

Mr Hague, who greeted US Secretary of State John Kerry, added that humanitarian aid, while indispensable, would not solve the Syrian crisis by itself.

“We certainly believe that it’s necessary to continue, if the situation keeps deteriorating, to increase the practical help we give to the Syrian opposition,” he said.

It also emerged that leaders of the Syrian National Coalition, the group representing the nation’s opposition forces, would be present on the sidelines of the G8. The rebel leaders were expected to meet at least the French and American foreign ministers — but also others willing to see them.

The summit will see both Britain and France once again pressing the case for amending or lifting an arms embargo on Syria to support the outgunned rebels.

Paris and London say they want to raise pressure on Assad and try to force him to the negotiating table by allowing the supply of arms to the rebels.

The civil war in the Middle Eastern country has now been raging for two years and has already claimed an estimated 70,000 lives and displaced millions more.

Also high on the G8 agenda will be how to respond to threats from North Korea of an imminent conflict with South Korea.